INTERVIEW QUESTIONS FOR CHEMICAL ENGINEERING PSUs

[su_tabs style=”default” active=”1″ vertical=”no” class=””] [su_tab title=”BASICS” disabled=”no” anchor=”” url=”” target=”blank” class=””][su_expand more_text=”Unit operation” less_text=”Useful Physical changes occur in the chemical industry is known as a Unit Operation.
Example: Distillation, Filtration, Drying, Extraction, Gas absorption, Crystallization, etc. ” height=”100″ hide_less=”no” text_color=”#333333″ link_color=”#0088FF” link_style=”default” link_align=”left” more_icon=”” less_icon=”” class=””] [/su_expand]

[su_expand more_text=”Unit process” less_text=”Useful Chemical changes with or without physical change occur in chemical industry are
known as a Unit Process.
Example: – Oxidation, Reduction, Alkylation, Sulfonation, Chlorination, etc. ” height=”100″ hide_less=”no” text_color=”#333333″ link_color=”#0088FF” link_style=”default” link_align=”left” more_icon=”” less_icon=”” class=””] [/su_expand]

[su_expand more_text=”Boiling Point and Bubble Point.” less_text=”Boiling Point: -It is a temperature of a liquid at which the vapour pressure of the liquid is
equal to atmospheric pressure.
Bubble Point: -It is a temperature at which first bubble of vapour is formed. ” height=”100″ hide_less=”no” text_color=”#333333″ link_color=”#0088FF” link_style=”default” link_align=”left” more_icon=”” less_icon=”” class=””] [/su_expand]

[su_expand more_text=”When does liquid boil?” less_text=”When the vapour pressure of the liquid is equal to atmospheric pressure at that time liquid
is boil.” height=”100″ hide_less=”no” text_color=”#333333″ link_color=”#0088FF” link_style=”default” link_align=”left” more_icon=”” less_icon=”” class=””] [/su_expand]

[su_expand more_text=”Acetone and water out of this which is more volatile and why?” less_text=”Acetone is more volatile than water because of boiling point of acetone
(56.7 °C) is low compa re to boiling point of water (100° C)” height=”100″ hide_less=”no” text_color=”#333333″ link_color=”#0088FF” link_style=”default” link_align=”left” more_icon=”” less_icon=”” class=””] [/su_expand]

[su_expand more_text=”Why is Reflux done in distillation column? and Define Reflux Ratio.” less_text=”For Increasing product purity.
Reflux: -It is amount of distillate which is resend to distillation column is known as a
reflux.
Reflux Ratio: -Reflux ratio is the ratio of the portion of the overhead liquid product from
a distillation column that is returned to the upper part of column to the portion of liquid
collected as distillate. ” height=”100″ hide_less=”no” text_color=”#333333″ link_color=”#0088FF” link_style=”default” link_align=”left” more_icon=”” less_icon=”” class=””] [/su_expand]

[su_expand more_text=”What is effect of reflux ratio on the no. of plate required in distillation column?” less_text=”At high reflux ratio no. of plate required less (Small column height) and at low reflux
ratio no. of plate required more (Large column height). ” height=”100″ hide_less=”no” text_color=”#333333″ link_color=”#0088FF” link_style=”default” link_align=”left” more_icon=”” less_icon=”” class=””] [/su_expand]

[su_expand more_text=”Unit operation” less_text=”Useful Physical changes occur in the chemical industry is known as a Unit Operation.
Example: Distillation, Filtration, Drying, Extraction, Gas absorption, Crystallization, etc.” height=”100″ hide_less=”no” text_color=”#333333″ link_color=”#0088FF” link_style=”default” link_align=”left” more_icon=”” less_icon=”” class=””] [/su_expand]

[su_expand more_text=”Define Distillation, Simple distillation, Steam distillation, vacuum distillation,
Azeotropic distillation, Extractive distillation and Fractional distillation?” less_text=”Distillation: – Distillation is unit operation in which liquid mixture is separated based on
their boiling point difference and relative volatility by means of thermal energy.
 Simple Distillation: – when the boiling point difference of two liquid in mixture is high
then we can use simple distillation.
Ex: – A mixture of acetone (B.P. – 57 ˚c) & water (B.P. – 100 ˚c) can be separated by
simple distillation because boiling point difference is high.
 Steam distillation: – Steam distillation is used for
– Separating high boiling components from Nonvolatile impurities by using steam.
– For separating high boiling fraction where there are chances of decomposition of material
at high temperature.
 Vacuum Distillation: – It is the type of distillation in which the liquid mixture is to be
distilled out in the vacuum which is less than the atmospheric pressure.
 Azeotropic Distillation: – (When Boiling point difference is very low) In Azeotropic distillation a third component called entrainer is added to the mixture which
forms a new low boiling azeotrope with one of the components which is distilled out first.
Ex – Acetic acid (B.P. – 115 ˚c) and water (B.P. – 100 ˚c) mixture, the butyl acetate (B.P. –
90 ˚c) is added as entrainer and it forms azeotrope with water in the mixture. Water and butyl
acetate is distilled out while acetic acid is remain as residue.
 Extractive Distillation: – Also used when boiling point difference is very close
In Extractive distillation solvent is added which alter the relative volatility of the original
components, thus permitting separation.
Ex – In Toluene (B.P – 111 ˚c) and Iso-octane (B.P. – 100 ˚c) liquid mixture, phenol (B.P. –
182 ˚c) is added as solvent, Iso-octane is removed as distillate and toluene and phenol
removed as residue.
 Fractional Distillation: – It is used for separating more than two components from the
liquid mixture
Ex – Crude oil
NOTE:……………………………………………” height=”100″ hide_less=”no” text_color=”#333333″ link_color=”#0088FF” link_style=”default” link_align=”left” more_icon=”” less_icon=”” class=””] [/su_expand]

[su_expand more_text=”What is principle of vacuum distillation & Define Vacuum?” less_text=”Vacuum is pressure less than atmospheric pressure, when it is applied at that time liquid boils
before its boiling point.
Vacuum: – Pressure below the atmospheric pressure is called vacuum.” height=”100″ hide_less=”no” text_color=”#333333″ link_color=”#0088FF” link_style=”default” link_align=”left” more_icon=”” less_icon=”” class=””] [/su_expand]

Difference between drying and

evaporation

[su_expand more_text=”Name any four dryers along with one application in each case.” less_text=”1. Tray Dryer: -used in dyes and pharmaceuticals industry.
2. Spray Dryer: -used in detergent and food industry.
3. Fluidized Bed Dryer (FBD): – used in pharmaceuticals industry.
4. Rotary Dryer: -Cement industry.
5. Roto Cone Vacuum Dryer(RCVD): -Pharmaceuticals industry.” height=”100″ hide_less=”no” text_color=”#333333″ link_color=”#0088FF” link_style=”default” link_align=”left” more_icon=”” less_icon=”” class=””] [/su_expand]

[su_expand more_text=”Write difference between single effect and multiple effect evaporator.” less_text=”In multiple effect evaporator vapour coming out from 1st evaporator is use as feed for
2nd evaporator. While in single effect evaporator vapour coming out from evaporator is
going to condenser and discard.
 Cost of multiple effect evaporator is higher than single effect evaporator.
 Multiple effect evaporator is use in large scale operation” height=”100″ hide_less=”no” text_color=”#333333″ link_color=”#0088FF” link_style=”default” link_align=”left” more_icon=”” less_icon=”” class=””] [/su_expand]

Write difference between Forward feed and Backward feed evaporation

[su_expand more_text=”. Define Humidity. Write the name of one equipment use for measuring humidity.” less_text=”Humidity is the amount of water vapour in the air.
Relative Humidity: – It’s the ratio of the amount of moisture in the air to the maximum
amount of moisture that could exist in the air at a specific temperature.
Specific Humidity: – It’s the ratio of the mass of moisture in the mixture to mass of moisture
in air.
Measuring equipment: – Hygrometer
Hydrometer: -A hydrometer is an instrument that measure the specific gravity (relative
density) of liquid.” height=”100″ hide_less=”no” text_color=”#333333″ link_color=”#0088FF” link_style=”default” link_align=”left” more_icon=”” less_icon=”” class=””] [/su_expand]

[su_expand more_text=”Define Saponification. ” less_text=”When an oil or fat is boiled with a solution of caustic soda, the resultant product are soap
and glycerin. The chemical reaction is called saponification.
Oil + caustic soda ——→ soap + glycerin” height=”100″ hide_less=”no” text_color=”#333333″ link_color=”#0088FF” link_style=”default” link_align=”left” more_icon=”” less_icon=”” class=””] [/su_expand]

[su_expand more_text=”Define Fire Point and Flash Point. What is the importance of determination of Fire
Point?” less_text=”Flash Point: – It is the lowest temperature at which vapour of fluid will produce a flash
by open flame.
Fire Point: -It is the lowest temperature at which the vapour of fluid will continue to burn
for at least 5 seconds after ignition by open flame. ” height=”100″ hide_less=”no” text_color=”#333333″ link_color=”#0088FF” link_style=”default” link_align=”left” more_icon=”” less_icon=”” class=””] [/su_expand]

. Name any four type of pipe fitting & it’s application.

[su_expand more_text=”Define: -Conduction, Convection & Radiation?” less_text=”Conduction: – It is heat transfer from one body to another body which is in physical
contact with it .it is restricted to solid.
Eg. Heat flow through wall of furnace
Convection: – It is heat transfer from one point to another point within a fluid by mixing
of hot & cold portion of fluid. It is restricted by fluid. (liquid & gas)
Eg_ heating of water in beaker
Radiation: – It is heat transfer from one body to another body by electromagnetic
waves., which not in contact with it, it is not required any medium.
Eg. Heat flow from sun to earth.” height=”100″ hide_less=”no” text_color=”#333333″ link_color=”#0088FF” link_style=”default” link_align=”left” more_icon=”” less_icon=”” class=””] [/su_expand]

[su_expand more_text=”Give full form of COD, BOD, TDS, PPM, CGMP & GMP.” less_text=”COD-Chemical Oxygen Demand
The amount of oxygen present in water consume during two hrs by the organic and
inorganic contaminant
BOD-Biological Oxygen Demand
BOD is the amount of dissolve oxygen needed by biological organism to break down
organic material present in one liter water during five days at 20 degree Celsius.
TDS- Total dissolved solid
PPM- Parts per million
CGMP-Current good manufacturing practice.
GMP-Good manufacturing practice.
GLP-Good laboratory Practice.” height=”100″ hide_less=”no” text_color=”#333333″ link_color=”#0088FF” link_style=”default” link_align=”left” more_icon=”” less_icon=”” class=””] [/su_expand]

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Comparing reciprocating & centrifugal pump: –

[su_expand more_text=”Define Cavitation in pump? How can remove cavitation?” less_text=”If the pressure in the suction line is less than the vapour pressure of the liquid some of the
liquid flashes into vapour creating gas pockets is called…
& it’s remove by priming & increase suction pressure head.” height=”100″ hide_less=”no” text_color=”#333333″ link_color=”#0088FF” link_style=”default” link_align=”left” more_icon=”” less_icon=”” class=””] [/su_expand]

[su_expand more_text=”Why are fins used in heat exchangers?” less_text=”To Increase Surface area. ” height=”100″ hide_less=”no” text_color=”#333333″ link_color=”#0088FF” link_style=”default” link_align=”left” more_icon=”” less_icon=”” class=””] [/su_expand]

[su_expand more_text=”Why are multipass heat exchanger are used in industry?” less_text=”The multipass provides more heat transfer in given space. This type of heat exchanger
consists of a shell with a bundle of tubes inside it. ” height=”100″ hide_less=”no” text_color=”#333333″ link_color=”#0088FF” link_style=”default” link_align=”left” more_icon=”” less_icon=”” class=””] [/su_expand]

[su_expand more_text=”how hard water can be softened? ” less_text=” by zeolite process
 ion exchanger requires
 lime softening
 reverse osmosis
 on boiling” height=”100″ hide_less=”no” text_color=”#333333″ link_color=”#0088FF” link_style=”default” link_align=”left” more_icon=”” less_icon=”” class=””] [/su_expand]

[su_expand more_text=”When do you use gear pump?” less_text=”The gear pump is commonly used in the chemical industry for handling high viscosity
liquids including molasses, paints, and greases.” height=”100″ hide_less=”no” text_color=”#333333″ link_color=”#0088FF” link_style=”default” link_align=”left” more_icon=”” less_icon=”” class=””] [/su_expand]

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